1. Field of the Invention
The present invention relates to a method and apparatus for accumulating energy from an oscillating column of water.
2. Description of Related Art
Electrical generators that harness the power of an oscillating water column have been known for at least a number of decades. In general, these generators include a large chamber built at the shoreline of a body of water, the chamber both rising above and submerging below the water level at the shoreline. Such chambers are typically built along steep shorelines, or even into the faces of cliffs, where the difference in height between wave crests and wave troughs is pronounced.
The chamber includes a first opening submerged below water level and a second opening that vents to the atmosphere via a turbine, such that the chamber contains a column of water having a height approximately equal to the water level outside the chamber. As the crests and troughs of waves arrive at the chamber, the level of the water column within the chamber periodically rises and falls, thereby alternately forcing air within the chamber to vent through the turbine into the atmosphere and drawing air from the atmosphere back through the turbine to the chamber.
Although ingenious, these generators suffer from a number of disadvantages. First, the corrosive mixture of salt water and air typically found inside the chamber can cause parts, for example the turbine, to wear prematurely. Second, a turbine, which is a relatively expensive component, is required to harness the energy of each such water column; in other words, if a series of such chambers were constructed side-by-side, each would require its own turbine because of the difficulty of synchronizing the chambers' air-flows so as not to interfere with each other. Third, the bi-directional airflow pumped by the oscillating water column conventionally demands a self-rectifying turbine, typically a Wells turbine, which is generally less efficient than a non-rectifying turbine, particularly under large and small wave conditions.
Accordingly, what is needed therefore is a method and apparatus for accumulating energy from one or more oscillating water columns that is less subject to the above disadvantages.